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Re: [Qemu-devel] [PATCH v2 1/9] nbd: Allow unmap and fua during write ze


From: Max Reitz
Subject: Re: [Qemu-devel] [PATCH v2 1/9] nbd: Allow unmap and fua during write zeroes
Date: Thu, 17 Nov 2016 22:10:26 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.4.0

On 17.11.2016 21:13, Eric Blake wrote:
> Commit fa778fff wired up support to send the NBD_CMD_WRITE_ZEROES,
> but forgot to inform the block layer that FUA unmapping of zeroes is
> supported.  Without BDRV_REQ_MAY_UNMAP listed as a supported flag,
> the block layer will always insist on the NBD layer passing
> NBD_CMD_FLAG_NO_HOLE, resulting in the server always allocating
> things even when it was desired to let the server punch holes.
> Similarly, failing to set BDRV_REQ_FUA means that the client may
> send unnecessary NBD_CMD_FLUSH when it could have instead used the
> NBD_CMD_FLAG_FUA bit.
> 
> CC: address@hidden
> Signed-off-by: Eric Blake <address@hidden>
> ---
>  block/nbd-client.c | 4 ++++
>  1 file changed, 4 insertions(+)

Reviewed-by: Max Reitz <address@hidden>

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